The benefits of a wireless communication network are readily recognized. The ability to transmit and receive either voice or peripheral (i.e., facsimile) messages in mobile applications has been utilized in numerous applications.
Wireless communications systems include cellular systems which have particularly enjoyed expansive popularity. Cellular systems generally comprise a base station and a plurality of portable stations. Cellular systems offer a radius of approximately 1-15 km per base station, and traditionally provide coverage for cities, railways and main roads. However, existing cellular systems typically utilize a service network which is distinct from the existing network (e.g., Public Switched Telephone Network (PSTN) or Integrated Services Digital Network (ISDN)).
Other wireless communication protocols have been introduced to provide benefits over existing cellular wireless technologies. Such communication protocols provide benefits of interfacing directly with and utilizing the existing digital network. Such direct interfacing capabilities eliminate the need for a distinct switching system.
One such communication system is the personal handy-phone system (PHS). The personal handy-phone system is a digital cordless telephone system that offers integrated telecommunication services, such as voice and data, via a universal radio interface. The personal handy-phone system offers digitalization of the communication system. In particular, the digital personal handy-phone system offers improved quality and effective use of frequencies.
Personal handy-phone systems comprise at least one base station and a plurality of corresponding personal stations. The personal handy-phone system offers flexible inter-connectability wherein connection of a personal station with a plurality base stations at various locations such as the office, home, or outdoors is possible. The PHS standard is set forth by the Telecommunications Technical Committee of Japan in "Personal Handy Phone System", Japanese Telecommunications System Standard, RCR-STD 28.
The personal handy-phone system also offers connectability with existing communications networks. Connection is possible with analog telephone networks as well as digital networks.
Personal handy-phone systems typically comprise a plurality of personal stations (PS), also referred to as handsets, and base stations, also referred to as cell stations (CS). Personal handy-phone systems are designed to provide wireless multimedia communications, terminal mobility, and complete two way communications. Personal handy-phone systems utilize a micro-cell structure. Personal stations and base stations of the personal handy-phone system are configured to transmit and receive data via a plurality of data packets, also referred to as slots.
The base stations may be of a low power output type (i.e., 10 mW) generally for indoor applications, or a standard power output type (i.e., 20 mW) or high power output type (i.e., 100-500 mW) for outdoor applications. Group control functions may be implemented to increase communication channels in an area with heavy traffic whereby multiple base stations acre controlled via the same control channel. Such stations may be arranged in a master/slave configuration.
Radio interfaces of the base stations and personal stations individually have four-channel time division multiple access capability with time division duplexing (four-channel TDMA-TDD). The implementation of TDMP, and TDD in accordance with the personal handy-phone system communication standard necessitates synchronization of the personal stations and the corresponding base station.
Individual base stations are synchronized with the appropriate telecommunications network to ensure reliable communications therebetween. Individual ones of the slave base stations are synchronized with the master base station in master/slave configurations.
Reference signals provided by conventional telecommunication networks (e.g., Integrated Services Digital Network) are typically unreliable inasmuch as phase drift is frequently experienced in such reference signals. Further, other reference signals may also experience phase drift during communications between the devices. It is preferred to periodically analyze the synchronization of the communication devices to verify the correct timing of the devices and compensate for phase drift.
Conventional synchronization techniques utilize hard-wired circuitry to compensate for phase drift and assure synchronization. However, these techniques are designed for a specific use and fail to provide flexibility to support a plurality of applications.
Therefore, there exists a need for assuring synchronization of the communication stations of a personal handy-phone system and providing flexibility for assuring synchronization in a plurality of applications.